Where helicopters are designed with a single main rotor for providing lifting forces, they must be provided with means for counteracting the torque exerted by the main rotor upon the helicopter body. This is conventionally done with a tail rotor mounted to the helicopter tail boom or vertical fin for rotation within a vertical plane. Should the tail rotor malfunction, the torque developed by the main rotor ceases to be counteracted properly by the tail rotor. In this event the helicopter body may start to rotate about the main rotor axis which, where the malfunction is severe, can produce an uncontrollable situation that can result in the helicopter crashing. Tail rotor malfunction may arise from mechanical failure. In military operations such a malfunction can result from damage inflicted by enemy fire upon the tail rotor or upon the tail rotor drive transmission system.
Helicopters have been devised with other means for providing anti-torque forces to the helicopter body or fuselage. For example, as shown in U.S. Pat. Nos. 2,518,697 and 4,200,252, helicopters have been designed with ducts and baffles for channeling airstreams to and about the tail boom to produce anti-torque forces in counteracting main rotor torque. Though such designs obviously eliminate the need for a tail rotor itself, they have their own problems and limitations and, of course, do not provide an emergency system for counteracting the loss of anti-torque forces for those types of helicopters that do have tail rotors.
Accordingly, the present invention is directed to systems and methods for providing emergency anti-torque control for helicopters of the type that have a tail rotor in the event of tail rotor malfunction.